Since human kind first began to employ tools, one of the most versatile and prolific tools has been the knife. Primitive humans used knives for piercing, cutting and scrapping. Here, knives were first formed of a stone material, such as quartz, flint or obsidian. The knife edge was created by pressure-flaking the stone along its crystalline cleavage planes with intersecting planes creating the cutting edge. While such technique resulted in extremely sharp edge, stone knives were brittle such that the edge was easily broken or chipped.
As technological advancement occurred, knives or other cutting blades began to be formed out of metal. Metal was less brittle and more malleable than stone. Thus, metal blades with cutting edges had the advantage of resistance to chipping. However, the cutting edges of metal blades were often not as sharp as stone edges and would tend to become dull with time and use unless resharpened. However, as technology developed into more modern times, the sharpness of metal edges began to approach the sharpness of stone edges; however, dulling remained a problem.
Recent developments in materials science, however, has resulted in high technology ceramic materials which, like their stone cousins, can form a matrix onto which an extremely sharp blade edge may be formed. Ceramic blade edges, however, still are subject to some chipping due to their brittleness. Materials traditionally used for forming ceramic blades include alumina and zirconia. Usually, a blade blank is formed by mixing a ceramic powder with a binder or plastisizer and compressing the mass under high pressure to create a solid cohesive mass. Typical particle sizes for such materials are on the order of 0.5 microns or less. The compressed material is typically fired in a furnace until it is hardened into a cured state. The cutting edge is formed on the material either before or after this hardening step.
In any event, ceramic cutting blades have many advantages over their metal counterparts. In addition to their extremely sharp edge, ceramic cutting blades can be readily sterilized, for example, when these blades are used as medical scalpels. Where employed in industrial applications, such as the semi-conductor industry, there is less risk of contamination from the ceramic material since it is rather benign to the semiconductor doping process. Metal, on the other hand, can contaminate and ruin the semi-conductor materials.
There have been some attempts to advance the art of ceramic blades in recent years. One such example is shown in U.S. Pat. No. 5,077,901 issued Jan. 7, 1992 to Warner et al. In this patent, a ceramic blade and production methodology is described. The blade includes a cutting edge formed by first and second cutting faces oriented at a bevel angle. At least one of the cutting faces includes striations having a grain direction substantially perpendicular to the cutting edge with these striations having a width of between 20 and 40 microns. These striations have benefits including increase blade endurance. Further, micro-chipping of the material is described as causing the material between adjacent striations to slough in a direction perpendicular to the edge. The “pressure flaking” during use tends to increase the sharpness of the cutting edge as opposed to diminishing the sharpness.
Despite the advantages achieved by the ceramic blades in the '901 Patent, there remains a need for increasingly improved ceramic cutting blades. There is a need for ceramic blades that can be used in medical and industrial applications as well as blades that may be used for consumer products, such as razor blades. There is a need for such ceramic blades that have increased sharpness and enhanced durability while at the same time can be produced by a methodology that is cost effective and within the economic reach of the ordinary, average consumer.